It was not a rhetorical question, though it may have seemed like one. As the Celtics prepared Friday morning to face the Golden State Warriors that night, coach Doc Rivers wondered aloud, “How many times have they been zoned?” The answer was about what one would expect against a squad like the Warriors, who have arguably the league’s top shooting backcourt in Stephen Curry and Klay Thompson. Not surprisingly, assistant coach Kevin Eastman found, the Warriors had faced a zone defense a sum of 70 minutes this entire season. Defending an excellent shooting team with a zone, after all, is almost always a bad idea. In the spirit of genius moves being spurred by necessity, the Warriors forced Rivers’ hand and he responded with a masterstroke. With Avery Bradley picking up his fifth foul early in the third quarter and Courtney Lee dealing with foul trouble of his own, Rivers essentially tossed the zone out on the court and told the Warriors: Solve this. They could not. Curry, fresh off a 54-point performance in Madison Square Garden, was held to 6-of-22 shooting overall and missed eight of his 11 attempts from 3-point territory. Thompson was 7-for-19 from the field and 1-for-7 beyond the arc. All together the Warriors shot 34 percent against the Celtics, clanging their way to a 94-86 defeat at TD Garden. “It was a different look,” Kevin Garnett said of the zone. “Against good shooting teams, you’ve got to be very, very talkative when you go zone. I was kind of wary of it, but it was a different look. I thought it was a great call on Doc’s part. He and [assistant coach] Mike [Longabardi] made a great call and it slowed them down. I thought they went to a more individual game and that played in our favor.”